Need help diagnosing rumble at idle after spark plug change

ren · 12-14-2010, 08:32 PM

My car has 23K miles and I have had Procede for 15K miles, so I decided to change my spark plugs even though I didn't have any problems. Since I had to remove the cowling for that, I also did the optional Procede harness fix and reset adaptations. I didn't have any codes, but the car rumbled at idle when the engine was warm, similar to k726's case here: http://www.e90post.com/forums/showpo...66&postcount=1. This is not like the common rough idle I had before, it is more noticeable as if some fat ass is shaking the car.

I drove the car for maybe 100 miles since then, and it still has the same thing. And still, no codes, no misfires. I can only feel it when the engine is warm and idle, and turning the AC off makes it more noticeable.

I reset adaptations one more time, and drove the car according to the TSB to do the readaptation, but still no luck. When I come back to my garage and let the car idle for a few minutes, it rumbles maybe once every 20 seconds, and the idle RPM goes up to around 800 and stays there until I turn the engine off.

This is what I can think of:
- Problem with one of the new spark plugs
- Problem with one of the coils, maybe not touching the plug all the way?
- I don't think it has anything to do with the Procede harness fix, but that's something I changed so I keep that in the list

I'm thinking of taking the spark plugs out, making sure that they look fine and put them back in.

Do you think cleaning up inside the coils with some contact spray would help?

Any ideas or suggestions?

Ilma · 12-14-2010, 10:56 PM

I recently changed my plugs and reset adaptations and I noticed this same "idle-stumble" right after.

No codes, but sometimes when it happens, the DME increases the idle goes up from 650 to 750 to smooth it out.

I don't know if it's the new plugs or the injectors, but it happened immediately after swapping the plugs.

And I cleaned the coil contacts and pressed down on them until I felt them hit the top of the spark plug.

ren · 12-15-2010, 06:55 PM

Maybe the ECU needs more time to adapt for a smoother idle, but then we would have seen other people having the same issue after changing the spark plugs.

12-14-2010, 08:32 PM	#1
ren Captain 62 Rep 840 Posts Drives: 2024 X7 M60i Join Date: Jan 2007 Location: U.S. iTrader: (8)	Need help diagnosing rumble at idle after spark plug change My car has 23K miles and I have had Procede for 15K miles, so I decided to change my spark plugs even though I didn't have any problems. Since I had to remove the cowling for that, I also did the optional Procede harness fix and reset adaptations. I didn't have any codes, but the car rumbled at idle when the engine was warm, similar to k726's case here: http://www.e90post.com/forums/showpo...66&postcount=1. This is not like the common rough idle I had before, it is more noticeable as if some fat ass is shaking the car. I drove the car for maybe 100 miles since then, and it still has the same thing. And still, no codes, no misfires. I can only feel it when the engine is warm and idle, and turning the AC off makes it more noticeable. I reset adaptations one more time, and drove the car according to the TSB to do the readaptation, but still no luck. When I come back to my garage and let the car idle for a few minutes, it rumbles maybe once every 20 seconds, and the idle RPM goes up to around 800 and stays there until I turn the engine off. This is what I can think of: - Problem with one of the new spark plugs - Problem with one of the coils, maybe not touching the plug all the way? - I don't think it has anything to do with the Procede harness fix, but that's something I changed so I keep that in the list I'm thinking of taking the spark plugs out, making sure that they look fine and put them back in. Do you think cleaning up inside the coils with some contact spray would help? Any ideas or suggestions?
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12-14-2010, 10:56 PM	#2
Ilma Colonel 193 Rep 2,854 Posts Drives: 2023 M4 Competition Join Date: Nov 2008 Location: Mississauga iTrader: (0)	I recently changed my plugs and reset adaptations and I noticed this same "idle-stumble" right after. No codes, but sometimes when it happens, the DME increases the idle goes up from 650 to 750 to smooth it out. I don't know if it's the new plugs or the injectors, but it happened immediately after swapping the plugs. And I cleaned the coil contacts and pressed down on them until I felt them hit the top of the spark plug.
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12-15-2010, 06:55 PM	#3
ren Captain 62 Rep 840 Posts Drives: 2024 X7 M60i Join Date: Jan 2007 Location: U.S. iTrader: (8)	Maybe the ECU needs more time to adapt for a smoother idle, but then we would have seen other people having the same issue after changing the spark plugs.
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